The Ek2 of Cangdong Sag is dominated by depression-basin-type sedimentation. A set of fine-grained sedimentary rock has been stably developed in large areas in the main body of the lake basin, and mainly includes four major rock types: clay rock (with a grain size of less than 0.05 mm), fine-grained felsic sedimentary rock, fine-grained mixed sedimentary rock, and dolomite, with lamellation and texture development, collectively referred to as shale strata, with a high brittleness index. The closed lake basin which is relatively oxygen deficient and contains brackish water during the deposition period of the Ek2 is beneficial to the preservation and enrichment of organic matters in the middle of the lake basin. Three major types of rock can be used as reservoirs and also hydrocarbon source rock, with good organic matter types and high abundance, and conform to the good-very good level of hydrocarbon source rock according to comprehensive evaluation based on various indicators. Based on test analysis of a system cored well, an “iron pillar” of a seven-property relationship among source rock, lithology, electrical property, physical property, brittleness, oil-bearing probability and earth stress is established, and it is clear that seven sweet spot strata have developed in the longitudinal direction of the Ek2, in which the source and reservoir are integrated, with large-area joined oil-bearing characteristics. A favorable area of shale oil is 260 km2, with a resource quantity of about 680 million tons. The potential for shale oil exploration is great.
In recent years, multiple wells in the main body of the lake basin have produced industrial oil flow, which confirms that shale oil is a replacement resource for the next step of increasing reserves and production. However, there are also prominent problems. Shale oil vertical wells have a high yield in the initial stage, but generally have a rapid decline in production, and difficulty in stable yield. To this end, Dagang Oil Field actively promotes the geological and engineering integration in this area, explores the implementation of horizontal shale oil wells, in the hope of achieving stable and high production of shale oil, and lays a foundation for the establishment of a pilot area for efficiently increasing reserves and production of shale oil.
At present, the prospecting of shale oil in Dagang Oil Field and other exploration areas in China is still in the exploration and research stage. In implementations of optimal selection of shale oil horizontal wells, there is still a lack of a perfect technical series as a reference, and the optimal selection and implementation methods of conventional horizontal wells are not suitable for guiding the deployment of shale oil horizontal wells, so there is an urgent need for a research method of trajectory design and on-site tracking and adjustment of a shale oil horizontal well.